Surgical accuracy of the hand-held instruments depends on the active compensation of disturbance and tremor. Physiological tremor is one of the main causes for imprecision in micro-surgery procedures. One of the popular tremor compensation methods is based on weighted-frequency Fourier linear combiner (WFLC) algorithm, that can adapt to the changes in frequency as well as amplitude of the tremor signal. WLFC estimates the dominant frequency and the amplitude. For the case of tremor with frequency variation or comprising of two or three frequencies close in spectral domain, the WFLC performance is degraded. In this paper, we present a bandlimited multiple Fourier linear combiner that can track the modulated signals with multiple frequency components. We also discuss the tremor sensing with accelerometers. Using the proposed algorithm the drift caused by the accelerometers is also eliminated. The proposed filter is tested in real-time for 1-DOF cancellation of tremor.

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Active physiological tremor compensation instruments have been under research and development recently. The sensing unit of the instruments provides information on three degrees-of-freedom (DOF) motion of the instrument tip using accelerations provided by accelerometers placed inside the instruments. A complete vector of angular acceleration of the instrument needs to be known to obtain information on three DOF motions of the tip. Sensing resolution of angular acceleration about the instrument axis is directly proportional to the width of the proximal-end sensing unit. To keep the sensing resolution high enough, the width of the unit has to be made large. As a result, the proximalend sensing unit of the instruments is bulky. In this paper, placement of accelerometers is proposed such that the angular acceleration about the instrument axis need not be known to obtain information on the three DOF motions of the tip. With the proposed placement, the instrument is no longer bulky and fewer number of accelerometers is required, thereby making the instrument compact and better in terms of ergonomics and reliability. Experiments were conducted to show that the proposed design of placement works properly.

Probe-based confocal laser endomicroscopy (pCLE) provides high-resolution in vivo imaging for intraoperative tissue characterization. Maintaining a desired contact force between target tissue and the pCLE probe is important for image consistency, allowing large area surveillance to be performed. A hand-held instrument that can provide a predetermined contact force to obtain consistent images has been developed. The main components of the instrument include a linear voice coil actuator, a donut load-cell, and a pCLE probe. In this paper, detailed mechanical design of the instrument is presented and system level modeling of closed-loop force control of the actuator is provided. The performance of the instrument has been evaluated in bench tests as well as in hand-held experiments. Results demonstrate that the instrument ensures a consistent predetermined contact force between pCLE probe tip and tissue. Furthermore, it compensates for both simulated physiological movement of the tissue and involuntary movements of the operator's hand. Using pCLE video feature tracking of large colonic crypts within the mucosal surface, the steadiness of the tissue images obtained using the instrument force control is demonstrated by confirming minimal crypt translation.

With the increasing popularity of actuators involving smart materials like piezoelectric, control of such materials becomes important. The existence of the inherent hysteretic behavior hinders the tracking accuracy of the actuators. To make matters worse, the hysteretic behavior changes with rate. One of the suggested ways is to have a feedforward controller to linearize the relationship between the input and output. Thus, the hysteretic behavior of the actuator must first be modeled by sensing the relationship between the input voltage and output displacement. Unfortunately, the hysteretic behavior is dependent on individual actuator and also environmental conditions like temperature. It is troublesome and costly to model the hysteresis regularly. In addition, the hysteretic behavior of the actuators also changes with age. Most literature model the actuator using a cascade of rateindependent hysteresis operators and a dynamical system. However, the inertial dynamics of the structure is not the only contributing factor. A complete model will be complex. Thus, based on the studies done on the phenomenological hysteretic behavior with rate, this paper proposes an adaptive rate-dependent feedforward controller with Prandtl-Ishlinskii (PI) hysteresis operators for piezoelectric actuators. This adaptive controller is achieved by adapting the coefficients to manipulate the weights of the play operators. Actual experiments are conducted to demonstrate the effectiveness of the adaptive controller. The main contribution of this paper is its ability to perform tracking control of non-periodic motion and is illustrated with the tracking control ability of a couple of different nonperiodic waveforms which were created by passing random numbers through a low pass filter with a cutoff frequency of 20Hz.